The idea of managing mobility of a wireless device or mobile node on a network has been around for some time. Allowing a mobile node such as a cell phone or a personal digital assistant (PDA) to roam on the wireless network requires managing various equipment. When a mobile node passes from one radio tower to another radio tower, the mobile node can pass into areas of the network controlled by different equipment. At some point, to prevent the call from being disconnected or dropped, information is forwarded to the equipment that will be handling the call next so that the call can continue without interruption.
With the advent of Internet Protocol (IP), networks began sending data in packets and using an IP address to route the data to its final destination. In time, wireless networks started to become data capable and would assign an IP address to a mobile node for the purpose of sending data to the mobile node. Generally, interconnection between devices is standardized to a certain degree based on the International Organization for Standardization (ISO)'s definition of a model for Open Systems Interconnection (OSI). OSI is used to define modes of interconnection between different components in networking systems and uses a seven layer model to do so.
Among the seven layers, Layer 3(L3) is the network layer which is concerned with the delivery of packets of data. This layer defines the address structure of the network and how packets should be routed between end systems. IP and Internet Packet Exchange (IPX) are examples of network layer protocols. Layer 2 (L2) is the data link layer which also defines a lower level addressing structure for use between end systems as well as lower level framing and checksums which are used to transmit data onto the physical medium. Ethernet, Token Ring, and Frame Relay are examples of data link layer or L2 protocols. Typically, L2 switching is implemented alongside L3 routing for local area networks to facilitate communication between devices in a common IP subnet. However, in a wireless network where a mobile node can roam among base stations, handoffs can pose a problem in terms of security and continuity of data flow.
Mobile IP was introduced to allow a mobile node to keep the same IP address regardless of where the mobile node travels. When the mobile node is at home, it is on the home network, or the network with which it is typically associated. The router connected to the home network is the home agent. When the mobile node is away from the home network, it associates with a foreign network and communicates through a foreign agent. In the event that packets are sent to a mobile node, the packets first travel to the home network. If the mobile node is not residing in the home network the packets are forwarded to the foreign agent with which the mobile node is registered; and from the foreign agent, the packets are delivered to the mobile node.
Currently, the mobile node is involved in much of the mobility management required for handoffs in a Mobile IP implementation. With Mobile IP (MIP), typically a MIP stack is used to keep a permanent IP address with the mobile node, to assist in handoffs, and to provide a certain level of security between handoffs. The present invention moves much of the MIP stack functionality from the mobile node and handles the handoffs in a different manner.